How does Bogner get 80 watts out of a SHIVA?

[BrentSP]

I was talking with Doug at www.dougstubes.com about ordering tubes because my Shiva's clean is distorting and blew a fuse so I assume its the tubes (does anyone know?) Anyways we were talking and he was puzzled on how Bogner gets 80 watts to. He said Shiva's are very hard on the power tubes. He also owns a Shiva Depending on the manufacture of the EL34 they range from 25 - 30 watts a piece, but Bogner is rating their Shiva at 80 watts with 490 plate voltage...................Me don't understand.

[Heiko]

They cannot; at least not clean anyways! Amp companies do this wattage boasting thing a lot. This example is not as bad as Snider Amps lying about getting 30+ watts out of 2 EL84's.


Heiko

[John Phillips]

They might be getting close though, especially given that plate voltage.

I have on many occasions measured in excess of 70W RMS - continuous sinusoidal power, with no detectable clipping - from "50W" Marshalls, especially JCM800s which have higher plate voltage too.

Yes, they are pretty hard on the tubes.

Another way of 'increasing the power' is to measure the RMS but at a higher defined distortion level - say 5% not the usual 1%. This can then be correctly specified as an RMS power, and the difference is in the small print (which most buyers don't read anyway).

I'm not sure how much distortion you'd have to allow to gain those few extra watts, but probably not much - and with a tube amp, you tend not to hear low levels of distortion because it sounds nicer than a solid-state amp doing the same thing.

Many amp companies do the same thing, it's not actually outright lies, but you have to read the 'terms and conditions' .


Mesa claim 30W from two EL84s in the F-30 too. I actually talked to Randall Smith about this, he did admit that it's not a true RMS figure but is based more on 'peak' power, which their patented Dyna-Watt circuit maximises. I was still not very impressed...

I think 'rated power' should be a minimum, measured as continuous RMS at a defined frequency (eg 1KHz) and no, or low (eg less than 1%, which is commonly accepted) distortion. Otherwise the numbers can be pretty meaningless.

[hear and play]

Originally posted by John Phillips


...

I think 'rated power' should be a minimum, measured as continuous RMS at a defined frequency (eg 1KHz) and no, or low (eg less than 1%, which is commonly accepted) distortion. Otherwise the numbers can be pretty meaningless.

This would be a help in that it would allow direct comparisons across amps. However, I'd actually like to see it done in a more meaningful way: report the wattage and THD with the amp's volume control on 2, 5 and 10. I appreciate that what I'm getting is not just wattage but headroom and the taper of the volume control, but isn't that what guitarists really want to know?

[hunter]

I'm reminded of something Mitch Faber at Mesa-Boogie told me a long time ago when i inquired about all the different published wattage values for MK IIIs. "If it's way f**king loud, does it really matter?" In the case of the MkIII, I had to agree.

hunter

Originally posted by BrentSP
I was talking with Doug at www.dougstubes.com about ordering tubes because my Shiva's clean is distorting and blew a fuse so I assume its the tubes (does anyone know?) Anyways we were talking and he was puzzled on how Bogner gets 80 watts to. He said Shiva's are very hard on the power tubes. He also owns a Shiva Depending on the manufacture of the EL34 they range from 25 - 30 watts a piece, but Bogner is rating their Shiva at 80 watts with 490 plate voltage...................Me don't understand.

So...what tubes did you decide on? I'll probably have to do the same thing pretty soon to my EL34 Shiva...any words of wisdom from Doug about our Shiva situation?

[John Phillips]

Originally posted by hunter
"If it's way f**king loud, does it really matter?"

Yes it does IMO. It's still misleading marketing no matter how you pitch it.

FWIW, I agree completely with Randall Smith that the Dyna-Watt circuitry did indeed make the F-30 "sound like at least 30 watts" - in isolation, or for single-note, mid-voiced lead lines in a band mix (ie 'traditonal lead guitar'). This is because this type of sound benefits more from peak power than RMS.

But when trying to play full-voiced clean rhythm at band volume, it was not even close to as loud as a real 30 watt amp. RMS is what counts here. And (as you'll probably know by now ) I use a lot of effects - this same lack of true power made heavy fuzz/octaver sounds, or even very thick chorused/phased sounds totally mush out - again, at far lower volume than a genuine 30 watter.

It is in fact about 22W RMS (of course). Yes, I know that the difference is 'only' about 2dB, but that is night and day in a live mix - although it may not be very noticeable in isolation... like in the shop.

People need to know these things before they buy an amp - which by definition, they can't try on stage in the shop! If you want 30 watts, you should be able to buy 30 watts knowing you will get 30 watts. Period.

OK, speaker sensitivity makes a difference too, but more people are becoming aware of this now.


BTW (back to the point ) I remember that the old Orange 2-EL34 amps were rated at 80W too - but I don't think I've ever measured one with equipment accurate enough to tell what the true power was... except that they're incredibly loud.

I recently was experiencing a problem with my Shiva, which turned out to be a loose pre-amp tube.

I turned the amp over, with the intention of replacing the Chinese pre-amp tubes with Groove tubes ECC83's, that I already owned.

After discovering the problem, I replaced the tubes anyway, and am happy with the results. Groove tubes sells these tubes as an upper end tube, and with a Shiva, it will run at least $84 to re-tube.

This seemed to Remedy The some what Buzzy distortion the Shiva is accused of having.

Also the clean chanel seems to react better to my FD2 with the ECC83's.

By The way, I have a Marshall RE-issue plexi, that before I re-built it, was putting out 175 watts, stock!

Bob

[Shark Sandwich]

With all this talk about over-rating amp power, how about under-rating it. Bad Cat claims their 2 EL-34 Hot Cat is a 30 watt amp. Yeah, right.

[trisonic]

Here's a couple:

Carr Rambler: 2x 6l6 = 28 Watts (Claimed Cathode bias, Class A)

Carr Hammerhead: 2x EL34 = 25 Watts (Claimed Class A)

I think we need John Phillips to do a tour of US bootique houses to ascertain what is what.

Pete.

Originally posted by Shovelhead
My Shiva is running 510 to 525 plate voltage. The bias was set REALLY hot from the factory - pulling 60 millivolts at idle. I tried to bias the amp much colder, but the bias pot ran out of range.

After speaking to Bogner, it turns out that the early Shivas were biased really hot, but ended up having reliability issues with the tubes (duh!). He had me strap on a couple of resistors in the bias circuit, and now I'm able to set the bias to draw 38 milliamps per tube at idle.

I think the 70 to 80 watts that I keep hearing about may have been because the tubes were pushed SO hard. I consider it to be a 50 watt amp.

If you try and get more than 25W RMS a tube out of EL34 you are running out of spec for an old correctly spec'd tube (not taking in consideration the crappy tubes of today), it also depends on if they are talking RMS or Peak wattage, As far as bias you should set the idle of a typical push pull Class AB amp like Marshall Fender to 70% of the peak rated wattage of the tube, dont set bias by current since you need to know the voltage on the plate to figure out the wattage, go to Aikenamps.com, he has some good advice there.
Just changing the bias to lower the wattage isnt the right way to do it, you need to lower the B+ voltage or the screen voltage. If you just lower the current flowing thru the tubes you could be creating crossover distortion, have someone with a scope check your amp properly.

more than 25WRMS clean signal out of an EL34 is TOO MUCH unless you are playing at home, then you can rock out till your tubes fry cause they will

[John Phillips]

Many old-production EL34s are a lot tougher than they're supposed to be.

A lot of amps I've worked on produce way over 50W RMS in Class AB without appearing to be noticeably hard on tubes, although 80 really is pushing it.

I certainly commonly bench-test Marshalls in the 60-70W RMS per pair (over 100W peak) range which are perfectly reliable - and my 'final approval' test is to absolutely thrash the amp - every knob dimed, whether it sounds any good like that or not - into a dummy load for at least 5 minutes. No more than 10% of the tubes blow under this treatment, and most show no sign of stress at all.

And I worked on a Selmer Zodiac recently with the tubes idling at 31W each - and had been like that for at least 15 years of reasonably frequent, and occasionally hard, use. With Mullards - they were still in excellent order too - which might even have been the originals in the amp, I don't know!

Yes, running tubes colder, in order to increase the maximum output power while not frying the tubes at idle, can produce crossver distortion, but actually this doesn't usually occur until you get surprisingly low. The commonly accepted bias point of 70% max dissipation is a maximum, not a requirement - most amps will sound fine at down to 30% or sometimes even lower.

Just my experience. But I warranty my work and I have no fear of sending out amps putting out more than 50W RMS per pair (with good tubes, anyway).

Well You could be lucky but I say 50-60W is no big deal depending on the tube, but considering the new tubes these days you are pushing it to go over 500V on the plates without dropping the screen. Are you using a non inductive load while bench testing? Adjusting the bias without looking at the sine wave is well.... the wrong way to adjust power. Usually if I go much under 70% I see crossover distortion. It work pretty well for me. I have put philips old stock 6l6in an SLO that kicked it up to 110W from 85 with 5881 bias correctly. But remember th VHT power amps getting 90~100 per pair of KT88 with over 600V on the plates? Those things were real reliable they were blowing holes in the circuit boards cause that is just too much for the quality of new tubes and the screen resistors were mounted to the PCB

[John Phillips]

Originally posted by DRZ400
Are you using a non inductive load while bench testing? Adjusting the bias without looking at the sine wave is well.... the wrong way to adjust power.

I don't agree. IMO the right way to check for crossover distortion is by EAR. It doesn't matter in the slightest what it looks like on a scope, it's what the amp sounds like that counts.

I use an inductive load (Marshall Powerbrake) - on purpose, because it's closest to the load presented by a real speaker - I checked, with the Powerbrake, and it really is very close - which is what matters when the amp is in use.

This may be the 'non-scientific' way to do it, but I really think it is the right way. You do not listen to music with a scope, and a speaker is inductive. Why set an amp up for a set of conditions that differ from how it will be used?

[Scott Peterson]

My EL34 Shiva puts 525 volts on the plates; I bias it at idle at 38mA and it sounds perfect to me.

I don't care what it's putting out powerwise; just that it sounds good. It is indeed plenty loud.

I don't care if it is rated for 50, 80, or 100 watts on 2 EL34's; I care about what my ears say.